A coup d'état (French, golpe in Spanish and putsch in German), pronounced koo-deh-TAH (SAMPA: ku: deItA:), is the sudden overthrow of a government, usually done by a small group that just replaces the top power figures. It is different from a revolution, which is staged by a larger group and radically changes the political system. The term is French for "a sudden stroke, or blow, of a nation."

Tactically, a coup usually involves control of some active portion of the military while neutralizing the remainder of a country's armed services. This active group captures or expels leaders, seizes physical control of important government offices, means of communication, and the physical infrastructure, such as streets and power plants. The trick is making it stick.

Coups typically use the power of the existing government for its own takeover. As Edward Luttwak[?] remarks in his Coup d'état: A practical handbook: "A coup consists of the infiltration of a small but critical segment of the state apparatus, which is then used to displace the government from its control of the remainder." In this sense, use of military or other organized force is not the defining feature of a coup d'état. Any seizure of the state apparatus by extra-legal tactics may be considered a coup, according to Luttwak.

In the late 20th century coups occurred most commonly in developing countries, particularly in Latin America, Africa and Asia, but also in the Pacific (Fiji) and in Europe (Greece, Portugal, Spain, Soviet Union).
Since the 1980s, the coup has been seen somewhat less frequently. A significant reason is the general inability to resolve the economic and political problems of developing nations, which has made armed forces, particularly in Latin America, much more reluctant to intervene in politics. Hence, in contrast to past crises, the armed forces have sat on the sidelines through economic crises such as the Asian crisis[?] in Thailand in 1998 or the Argentina crisis[?] of 2002 and have tended to act only when the military perceives itself as institutionally threatened by the civilian government, as occurred in Pakistan in 1999.

Coups d'état have often been a means for powerful nations to assure favorable outcomes in smaller foreign states. In particular, the American CIA and Soviet KGB were well known for engineering coups in states such as Chile and Afghanistan. Such actions are substitutes for direct military intervention which can be kept secret from the domestic public to prevent their interference. The governments of France and Britain have been accused of engineering coups as well.

One form of military intervention which some regard as a coup d'état is the use of the threat of military force to remove a particularly unpopular leader. This has occurred twice in the Philippines. In contrast to previous coups d'état, the military does not directly assume power, but rather serves as an arbiter for civilian leaders.

breakthrough coups - In which a revolutionary army overthrows a traditional government and creates a new bureaucratic elite. Breakthrough coups are generally led by NCOs or junior officers and only happen once. Examples include China in 1911 and Egypt in 1956.

guardian coups - These coups have been described as musical chairs. The stated aims of this form of coup is to improve public order, efficiency, or to end corruption. There is usually no fundamental shift in the structure of power. Many nations with guardian coups undergo many shifts between civilian and military governments. Examples include Pakistan, Turkey, and Thailand.

veto coups - These coups occur when the army vetoes mass participation and social mobilization. In these cases the army must confront and suppress large-scale and broad-based opposition and as a result they tend to be repressive and bloody. Examples include Chile in 1973 and Argentina in 1975.

Coups can also be classified by the level of the military that leads the coup. Veto coups and guardian coups tend to be led by senior officers. Breakthrough coups tend to be led by junior officers or NCOs. In cases where the coup is led by junior officers or enlisted men, the coup is also a mutiny which can have grave implications for the organizational structure of the military.

There is also a category known as bloodless coups in which the mere threat of violence is enough to force the current government to step aside. Bloodless coups are so called because they involve no violence and thus no bloodshed. Napoleon accessed to the power that way in 1799. More recently, Pervez Musharraf of Pakistan came to power in such a manner in 1999.

After the coup, the military is faced with the issue of the type of government to establish. In Latin America, it was common for the post-coup government to be led by a junta, a committee of the chiefs of staff of the various armed forces. A common form of African post-coup government is the revolutionary assembly, a quasi-legislative body made of members elected by the army. In Pakistan, the military leader typically assumes the title of chief martial law administrator.

According to Huntington, most coup leaders act under the concept of right orders: they believe that the correct approach to government is to issue correct orders. This view of government underestimates the difficulty in implementing government policy and the amount of possible political resistance to certain orders.